Culture optimization for protein expression in Escherichia coli

Abstract:

[Objective] Escherichia coli is the best characterized system in every aspect, and it has been the most widely used host for the production of recombinant proteins. Furthermore, the high cell density culture (HCDC) has allowed production of various proteins with high yield and high productivities. Automation and miniaturization are key issues of high-throughput research projects in the post-genomic era. [Methods] We applied a new culture-complex auto-inducing media (CAI) for heterogenous protein expression in E. coli. The CAI is in accord with automation and miniaturization. To test expression efficiency in the CAI, we constructed seven different plasmids named p-1、p-2、p-3、p-4、p-5、p-6 and p-7. These plasmids were transformed into E. coli BL21 (DE3), then expressed in both LB and CAI. [Results] The expression levels of seven fusion proteins in CAI were four times greater than those in LB. To improve the expression level even more, we analyzed the composition of the CAI and optimized the culture. Through a series of changes we formed a new optimized culture (CAI-4). Comparing the expression levels of there fusion proteins (P-1、P-2、P-3) in CA, the expression levels of fusion proteins in CAI-4 were twice greater than the control.